1. Field of the Invention
The present invention relates to a light quantity adjustment device and method, and an exposure apparatus. More particularly, the present invention pertains to a light quantity adjustment device and method, wherein a quantity of light emitted from an exposure light source including a plurality of light emitting devices is adjusted with respect to each light emitting device, and to an exposure apparatus, wherein a quantity of light emitted from an exposure light source including light emitting devices is adjusted with respect each light emitting device, thereby permitting a photosensitive material to be exposed to the quantity-adjusted light.
2. Description of the Related Art
An organic field-effect light emitting device incorporating fluorescent organic substances in a light emitting layer, which is referred to as organic electroluminescence (EL) device, is easier to make than other types of light emitting devices, and can be formed in a thin, light weight structure. In view of such advantages, such light emitting devices have been researched and developed as devices for a thin display panel. Further, since high performance organic EL devices have recently been obtained, which rival light emitting diodes (LED) in terms of emission luminance, light emission efficiency, durability, and the like, research has been undertaken to apply such devices in exposure apparatuses for exposing a photoreceptor such as silver halide photoreceptor.
An exposure apparatus using organic EL devices comprises, as shown in FIG. 11, for example, a plurality of sets (two sets in FIG. 11) of device rows arranged in a secondary scanning direction, wherein each set of device rows include light emitting sections 80 emitting light in red (R), green (G) and blue (B) colors which are arranged on a color basis in a primary scanning direction. In FIG. 11, the light emitting sections are indicated by the reference numeral 80 with alphabet suffix R, G, B added for distinction.
Not only an organic EL device including a plurality of light emitting sections but also an exposure head incorporating a plurality of light emitting devices suffers from a drawback that the quantity of emission varies from device to device due to manufacturing tolerances, thus resulting in uneven exposure.
In order to solve the above drawback, JP-A No. 8-142406 has proposed a method for adjusting light emission intensity wherein a light emission intensity distribution of each light emitting device is measured; the measured distribution is sliced with a standard light emission intensity value and the width of light emission intensity for each device is calculated; and an adjustment value for the driving energy is set so that each light emitting device represents an equal width of light emission intensity.
Further, JP-A No. 10-811 has proposed a technology for adjusting a quantity of light of each light emitting device, wherein a density distribution of a solid image (patch image) recorded on a photosensitive material is measured; then adjustment data is obtained to make constant the density value for each light emitting device; and the quantity of light emitted from each light emitting device is adjusted.
However, there is a problem that equalizing the luminescence intensity width of each light emitting device cannot prevent uneven exposure, since the obtained density distribution of the image becomes continuous with a continuous gradation photosensitive material such as silver halide photosensitive material. Another problem is that although the uneven exposure can be prevented with a continuous-gradation photosensitive material if adjustment is made so that the density value of the solid image becomes constant, the density distribution of a fine image must be measured with a high degree of precision, which requires very expensive measuring instrument, resulting in an increase in cost.